1. Field of the Invention
The present invention relates a store and forward messaging system. More particularly, the present invention relates to a method for initiating a session in a store and forward messaging system that saves transcoding resources for the system.
2. Related Art
A conventional video telephony session (e.g., video conferencing) includes a session initiation between two telephony devices. As part of the session initiation, the two telephony devices exchange their capabilities (e.g., via H.245 or SIP) and then utilize one or more algorithms to agree on the codecs and/or video size or colors to be used for that session.
For example, one telephony device may declare that it supports Adaptive Multi-Rate (AMR) audio codec and video codecs H.263 and MPEG4 while the other telephony device may declare that it supports audio codec AMR but for video codec only supports H.263. In such a situation, the audio codec during the session will be selected as AMR and the video codec will be selected as H.263.
In a store and forward system, such as a Voice/Video Call Answering (VCA) system, the scenario is somewhat different because the session is considered to be “indirect.” The session is considered to be indirect because the two telephony devices are never directly connected to one another. In this type of indirect system, the user calling the store and forward system to deposit a message is defined as a “guest” and the user of the store and forward system for whom the message is being deposited is defined as a “subscriber.”
Thus, in a VCA system, rather than the guest creating a session directly with the subscriber, the guest creates a session with the VCA system. After the session is created, the VCA system saves the message left by the guest. Then, at a later point in time, the subscriber can dial into the VCA system and retrieve the message.
For example, using the same scenario described above in which the guest telephony device supports video codecs H.263 and MPEG4, and the VCA system also supports video codecs H.263 and MPEG4, the session may utilize MPEG4 for the choice of video codec and thus the VCA system will store the message using MPEG4. However, if the subscriber dials into the VCA system using an H.263 only telephony device, the VCA system must transcode (i.e., convert) the message stored in MPEG4 format to the H.263 format which is required by the subscriber's telephony device (prior to playing the message to the subscriber).
Depending on the network behavior, and the capabilities of the subscriber's telephony device, the amount of transcoding required may be quite significant, thus requiring a great deal of hardware. In addition, the required transcoding may cause a significant degradation of the audio and/or video data being retrieved by the subscriber. Therefore, what is needed is a system and method in a store and forward system for reducing the amount of transcoding required when forwarding stored messages to a subscriber.